US Boobytrap Mechanisms

Firing Device, Pull, M1 Firing Device, Delay, M1
Designed during the Second World War, this is a fairly standard type pull switch.  Likely owes a lot of the design to the British No. 1 Mk. I Switch.  Remained in service and production for many years.  The device on the top is a WWII manufacture, on the bottom is a post war manufacture. This is a chemical delay igniter, very similar if not designed from the British No. 10.  The colored strips indicate the nominal delay times for each firing device.


Earliest version of Firing Device, Pressure, M1 Firing Device, Pressure M1
Developed from the British No. 2 Switch this device looks and operates in a similar manner but uses the American base coupling device instead of a spring snout like the 
British switch.
Also designed in the Second World War, this one owes a lot of its design to the earlier British No. 2 Mk. I pressure Switch.  It is the next in evolutionary design from the device shown above.  The top shows the device alone, the bottom photo shows it with the extension fitted to the pressure head.


Firing Device, Pressure, M1A1 Firing Device, Release M1
A modification of the M1 pressure device, this one is modified by having a threaded hole in the pressure head allowing a better attachment of the extension.  The top shows the firing device itself, the bottom shows a three pronged pressure adapter, also available were simple extension rods. Also designed during the Second World War, this device remained in service for many years afterwards.  Note the differences in the mounting brackets on the two devices.  The left photo is of a WWII manufactured device, the right is a post war manufacture.  There was not a change in nomenclature for this change.

Firing Device, Pull/Release, M3 Firing Device, Release M5
Designed during WWII, before 1943, this device has remained in service for many years, may still be in limited service.  Similar in design to the M1 pull switch, this one operates on either a pull or release of tension.  The upper photo is a WWII manufactured version, the bottom photo a post war version. Again designed in WWII, this release device was much smaller than the M1.  It remained in service for many years after the war.

Detonator, Concussion, M1 Firing Device, Combination, M142
This firing device was attached to explosive charges surrounding other explosive charges, so that when one was set off, the concussion of the blast would cause it to go off and likely to detonate yet another charge equipped with a concussion detonator.  It works on the diaphragm principle. This is an Australian Switch that has been adopted by the US and renamed M142.  It is now manufactured in the US.  Can be used in all  basic operating modes, pull, pressure, tension release, and release.

Firing Device, Delay, M147 AC Delay
This one of newest American firing devices.  It is electronic and can be set to fire between 5 minutes to 30 days.  Very reliable it cannot be turned off after a 5 minute safety elapses. Made and used by both the British and Americans, this switch was originally a British design.  The different coloured ampoules are what determines the delay time of the igniter.  Used with Limpet mines normally.

This particular one is of American manufacture.  The easiest method of telling the two apart is the thumb screw, Oval head is American manufacture, rectangular head is British.

Demolition Firiing Device, Mark 15 Mod. 0
Believed to be a US Navy device, used by UDT and Seal teams.  This is a delay device with a delay of up to 24 hrs.
M1 Friction Fuze Lighter M2 Fuze lighter
Drew sends this information.

The M1 holds the time fuse in place by teeth inside the fuse lighter. These teeth are inclined to permit time fuse to enter, but prevent its removal except by force. A loop or handle is provided at the closed end of the igniter to aid in ignition. To prevent pulling the fuse igniter from the fuse, which will cause an air gap between the fuse end and the igniter, hold the body of the igniter in one hand and pull the igniter wire with the other. If any doubt exists as to whether the fuse is burning and the length of the fuse will permit the time, pull the fuse igniter off the fuse by force immediately after pulling the igniter wire to verify time fuse is burning. The Fuse Lighter was introduced before the United States’ entry into WW II as an alternative means to igniting time fuse with a match (the most commonly used method of the time). While not weatherproof, it was more reliable and windproof than a match. By 1945 the M1 was in the process of being replaced by the M2 fuse igniter. A reliable igniter as far as function goes, but not completely weatherproof and therefore unreliable in inclement weather. In the earliest Army demolition manuals, employment as a firing device is shown with short lengths of time fuse. While not used in active service for decades, they are still being referenced in a 1996 U. S. Army technical manual, so they may still be in inventory.

Designed to replace the M1, this percussion type fuze lighter is much hardier than the cardboard bodied M1.  This one could also be waterproofed





M60 Fuze lighter Firing Device Mark 3
This is a fully waterproof type fuze lighter that works with a percussion cap to light the safety fuze. This is a 24 hour delay clock.  Produced for the OSS and US Navy near the end of WWII, (July 1944)  Only about 1500 of the 24 hour models were produced.  There was also a 12 hour delay model that was produced in larger numbers (20500).  Testing on an 8 day clock was also conducted but was not completed by VJ day and production and testing was ended.



The XM-81, which did become the current M-81, is a combination Modernized Demolition Initiator (MDI) device but it also replaces the M-60 fuse lighter.  To use in initiating MDI shock tube, the OD green plug is removed and the shock tube is inserted into the silicone collar and fired. 209 primer initiates the tube.  To use as a fuse lighter the OD green plug AND the silicone collar are removed, the M-700 fuse is inserted and the collar is tightened.